Meg, a troubled young karate student grappling with the tragic suicide of her sister, reluctantly joins a camping trip in the humid Japanese wilderness with four quirky acquaintances: the neurotic Maki, the vain and demanding model Aya, Aya’s sleazy boyfriend Nao, and their mild-mannered friend Kenta. Seeking emotional closure and escape, Meg instead finds a nightmare when they stop at a filthy public restroom. Here, they are suddenly ambushed by a horde of aggressive, mutated zombies born from a bizarre biological parasite that thrives on fecal matter and human waste.The grotesque creatures slaughter Nao in a sickening fashion, setting off a desperate fight for survival. As the group flees deeper into the marshlands, they cross paths with a disgraced scientist conducting illicit experiments involving the parasite, and a stoic, shotgun-toting American soldier named Professor Dan, who is hunting the infected. Dan explains the origin of the outbreak and reveals that Meg’s sister’s death was somehow tied to the early stages of this grotesque
biological contamination. Motivated by a desperate need for answers and vengeance for her sister, Meg taps into her suppressed
martial arts training, transforming from a grieving victim into a ferocious, kick-fighting warrior willing to endure unimaginable bodily fluids and violence to eradicate the undead.Tensions escalate as the survivors clash with a rival faction of heavily armed men who want to weaponize the parasite for global domination. Betrayals occur, and Aya is captured, transforming into a high-heeled, screeching zombie who must be put down by her former friends. The climax unfolds at a dilapidated sewage treatment facility where the mad scientist plans to unleash a massive wave of mutated zombie waste upon the populace. Meg, Kenta, and Professor Dan launch a chaotic, blood-soaked assault against the facility's guards and the surging hordes of feces-vomiting corpses. Utilizing martial arts, heavy weaponry, and sheer willpower, Meg confronts the primary mastermind in a brutal final showdown over a vat of toxic waste. She manages to defeat the villain, triggering a massive explosion that obliterates the laboratory and eradicates the parasite source. In the aftermath, Meg achieves the catharsis she desperately sought, finally at peace with her sister's memory as she walks away from the wasteland alongside the surviving Kenta, forever scarred by the horrifying events of the toilet apocalypse.